Field of the Invention
The present invention relates to power modules for reducing the space utilized by electronic components mounted on circuit substrates used for, for instance, controlling motors of industrial equipment or consumer equipment.
Description of the Background Art
A conventional power module, when driven, can generate an off-surge voltage. The power module can be damaged by the surge voltage if a voltage greater than a maximum rated voltage of the power module is applied to the power module. To reduce or eliminate the surge voltage, a film capacitor, called a snubber capacitor, needs to be mounted on a circuit substrate near the power module. Accordingly, a power module that has a capacitor embedded inside the power module has been proposed (for instance, see Japanese Patent Application Laid-Open No. 2007-151331 and Japanese Patent Application Laid-Open No. 2005-328651).
However, a high dielectric material used for capacitors is a sintered body. It is difficult to sinter a dielectric together with a lead at high temperature when a large capacitor in size is formed inside the conventional power module. As a result, such a large capacitor cannot be mounted inside the power module.
Further, the film capacitor that has a high breakdown voltage and a high frequency characteristic is large in size, and the film capacitor thus requires a large space when mounted on the circuit substrate. Hence, it is difficult to mount the large capacitor between the circuit substrate and the power module mounted on the circuit substrate. Because of this difficulty, the circuit substrate has a restriction where, for instance, tall electronic components need to be mounted on a surface opposite to a surface on which the power module is mounted. Accordingly, Japanese Patent Application Laid-Open No. 2011-67045 discloses an apparatus including a snubber capacitor outside a power module, for instance.
Although apparatuses described in Japanese Patent Application Laid-Open No. 2007-151331 and Japanese Patent Application Laid-Open No. 2005-328651 are configured such that capacitors are disposed inside power modules, as described above, it is difficult to dispose large capacitors in size inside the power modules.
Furthermore, the apparatus described in Japanese Patent Application Laid-Open No. 2011-67045 is configured such that the capacitor is disposed outside the power module, and that an electrode terminal is externally coupled between the power module and a circuit substrate. As a result, the electrode terminal unfortunately has a poor contact due to external stresses, such as vibrations.